Airplane cabin heating system



Dec. 10, 1946. HQESEL 2,412,334

AIRPLANE CABIN HEATING SYSTEM Filed July 10,1944 4 Sheets-Sheet 1 w & m

I'NVE/VTOR 42 45 4g; i fimq Dec. 10, 1946. HOESEL 72,412,334 AIRPLANE CABIN HEATING SYSTEM I Filed July 10, 1944 4 Shets-Sheet 2 Dec. 10, 1946. v I -A. F. HOESEL I AIRPLANE CABIN HEATING SYSTEM Filed July 10, 1944 4 Sheets-Sheet s v IINI/EIVITAOR Dec. 10, 19.46. A. F. HOESEL I AIRPLANE CABIN HEATING SYSTEM 4 Sheets-Sheet 4 Filed July 10, 1944 Patented Dec. 10, 1946 FFlf cE':

AIRPLANE CABIN HEATING sxs'rEM Anthony F. HoeseL Chicagmfilllt assignor to Peerless of America Inc., Chicago, 'IlL', a corporation of Illinois Application July 10, 1944, Serial No. 544,301

4 Claims.

The present invention relates to airplane cabin heating by utilizing the exhaust heat rejected by the engine.

Specifically, the invention is concerned with preventing the entrance of exhaust gases, in harmful quantity, to the airplane cabin if, for any reason whatsoever, the exhaust pipe proper should become perforated.

Present day highoctane fuels, at exhaust pipe temperatures, havea highly corrosive effect and eventually eat holes in the exhaust pipes, furthermore, in warfare, the possibility of bullet puncture is ever present. a

Previous exhaust heaters. always had the ever present danger, whenever perforated, of releasing lethal quantities of carbon monoxide into the cabin. Since carbon monoxide is a colorless, odorless gas one volume of which in 800 volumes of air will have fatal results if breathed for about 30 minutes, it is readily seen that protective measures thereagainstare not only desirable but imperative. I,

In great concentrations, such as would occur with a bullet punctured exhaust heater, the time of fatality, due to carbon monoxide poisoning, might be very short indeed and it is presumptive that certain unexplained fatalities have resultedv therefrom in planes so equipped.

An object of the present invention is to preventthe entrance of carbon monoxide, or exhaust gases, into, the airplane cabinwhenever theexhaust pipeof the heater is perforated.

Another object of the present invention is to automatically close down the heatin air supply to the airplane cabin whenever the exhaust. pipe of the air heater is perforated.

A further object of the present inventionisto provide an 'automatic signalling means to, indicate whenever the exhaust pipe of the air heater is perforated.

' .Other objects will appear in the following specification and claims. e

In the drawings:

Fig. 1 is across sectional view of a pressure reducing valve as may beused in the practice of the invention.

Fig. 2 is a cross sectional view of a pressure relief valve as may be usedinthe practice .of the invention.

a Fig. 3 is across sectional view along line 33 of 2. a

Fig. 4 i a cross sectional viewof theautomatic valve meansfor controlling the heated airflow, as y be e lm the nmcti e ef theinventio Fig. 5 is an end view of Fig. 4 in the direction of the arrow of Fig. 4..

Fig. 6 is a view, 'partly in section, of an auto-.- matic signalling means as may be used in the practice of the invention.

Fig. '7 is aview of a manually operated valve means for closing the air flow as may be usedin ed in a carrier 25,.against. which the spring 25 abuts and tends to urgethe ball valve 24 towards its seat. at the lower end of the bore 21 in which av pusher pinv 28 is a loose fit. The upper end of thepusher pin .28 abuts a diaphragm 25, which is clamped between the body 2| and the diaphragm spring. chamber 30 by means of the bolts 3 I. The spring support 32, mounted in the bore 33, is constantly urged against the diaphragm 29 byme'ans of the, spring 34, whose compressive strength is adjustable by means of the adjusting screw 35? which. has a lock nut. 36 for lockingithe same. Thediaphragm spring chamber 30 hasv a bore.3 8 whichallows theupper side of the diaphragm 2 9 to be. subjectedto theambint pressurefi] Assuming the spring 34 adjustedv to a given reduced pressure, at the outlet. 23, such reduced. pressure will, at all times, be reflected as apressure differential between. the ambient pressure and the reduced pressure, since the ambient pressure will, at all times and bymeans of bore 38, press upon, the upper side of the diaphragm 29. If the ambient pressure increases or decreases, the reduced pressure, at the outlet 23, will increase and decrease respectively by the same amount.

In Fi 2,,the pressure relief valve 4.0 comprises. a body '4'] having a chamber 42 with through. passages iii-land. 44. The boss. 45'has a bore 46 in which a valved! is place.d...and constantly urged away from its mating seat 48 by means. of the. valve spring 49. The bore.50 allows the escape of pressurafrom the chamber 42, Whenever the valve 4.] leaves its seat 48. The upper end, of

the valved], abuts a diaphragm 51 which is clamped betweenthe body 4i and the diaphragm. spring chamber 52 by means. of bolts. 53.. The. spring support 54. plays in the bore 55 and is.

strength is adjustable by meansof the adjusting screw 51, which has a lock nut 58 for locking the Thediaphragm spring chamber 52 has a sa a;

constantly urged against the diaphragm 5| by v means of the spring 56 whose compressive between the pressure conduit and the chamber 99 and transmits the pressure, and variations thereof, residing in the pressure conduit. Suspending from the body 86, and integral therewith, is a switch mounting lug I upon which is mounted a Micro switch IIJI by means'of screws ||l 2. These switches are so =universallyknown that it should suflice to state that a' slight move- -ment of the operating stem I03, abutting the tial between the ambient pressure and'the-pres'- ;'I- sure within the chamber 42; If the ambient pres- 1 increases, then the diaphragm 5| lifts upward allowing the valve 41 to openand relieve the ex-; cess pressure through the bore 50. If the chamsure remains constant and the chamber pressure I ber pressure is at a given valve and the ambient pressure decreases, then the total pressure, upon the, upperside of the diaphragm 5|, decreases and th'e diaphragm 5| and valve' l'l'move upwardlythereby, relieving the excess pressure different' ial through the bore 50. If the ambient pressure increases then the total pressure, upon the upper side of, the diaphragm 5|, increases 'and'there-- fore a greater pressure must occur, in the chamber"42,"before the valvejll will open.

In Figs. 4 and 5,1 showa hot air conduit 60 having journal bearings 6| in which the shaft 62 maybe oscillated. [A butterflywalve 63'is mounted 'upon'theshaft 62 and oscillated simul 'taneously therewithto either fullopenor full I closed positions (as-shown), by means of the crsnkarm 54. also mounted upon the shaft 62.

'fflljastened, to'the conduit 50, in some suitable manner or other, is a valve operator'65 comprisihg a' body 55' open toambient pressure, by

means" offbore 61, and having a boss 68 with a borelfis in.-which a push-pull rod 'IIl' 'canjreciprocate ""I he lower end, of the push-pull rod 10-, connectsto'the crank arm 1 64 by means of the floatinglinksll suitably pinned thereto as shown.'

1 The diaphragm support 12, riveted to the pushpull' rod'lll; as shown 'at'I3, is constantly urged,

' by meansof spring I4, ag ainst"'the diaphragm I5,

which is clamped, between the body 55 and the pressurejchamber cover lii having a conduit connectiqn bore 11, by means ,of'the bolts 18. The

spa e; 89, between the diaphragm I5 and the pressuref chamber cover'jlfi, defines a pressure tightfchamber, Wheneverthe pressure, in the push rod 9|, resultsin making or breakinganQ 'electriccircuit between the electric conductors IM. and/I05 connected to some suitable source of electrical energy,v

I'n'i the present" instance, the

ing stem I03 is'pushed upwardly, and breaks 7 1 the electrical circuit whenever the operating stem I53 -is in its downward position. The electrical"- conductor I04 has, in series circuit, a warning light lill or any other suitable warning means,

which is usually placed upon the instrument board in the pilot compartment.

Thebody 86 has a bore I58 allowing the dia-- phragm 93, upon its upper side, to be subjected to'the ambient pressure and all variations thereof, consequently any adjustment" of I the spring" Sit-is reflected in a given pressure differential chamberimjreduces to a certain value, the vari ous' elements" are in the positions shown since the spring 14, thenfexerts thepreponderant force."

Whenever the pressure, in' the chamber 80, excefedsa -certain value, the force of the spring I4 is'overcome' an d'the diaphragm I5 and the push-pull rod I0 then movedownwardly, compressing the springM, and move" the butterfly valve BQ'to wide open position thereby allowing an airflow through the hot air conduit 60. V In 'Fig; 6, an automatic signalling control 85 comprises a body 86 having a bore 8! threaded 'at the upper end 88 to engage anadjusting screw 85 serving :to vary the length and consequently thefpressure of the spring abutting thereagainst,

The pusher rod 9| has an enlarged diameter 92,

loosely mounted in the bore'8'l and'abutt'ed b'y the spring 9 0, which presses'against the "diaphragm 93 clamped between theibody 86 and the pressure chamber cover 94 by means of bolts 95.; 'I-he pressure chamber cover'has a conduit flare end-Q 96 T against which the pressure conduit is pressed" by the flar.e nut 9! thereby makinga pressure "tight joint. A bore 3 98' communicates necessary, in the chamber99'and on the underesideof the diaphragm 93, to;move the pusher rod 3| and the operating stem;|03, of the microswitch DI, to upward position thereby establish, ing' an electric circuit 'withinthe. conductors l 04;

and I55 and operating the signalling means I015" In Fig. '7, the hot: air conduit fill has agate means III) slidably mounted withina gate carrier Il I into, which it can be manually pushed in order 7 to stop any air circulation through the'conduit" 65. The gate III] is shown in open position'r In the manual operation, of, the invention, the auto maticsignalling means Fig, 6,,and the manually operated-valve means Fig. 7 would 'replacethe;

automatic valve means Figs. 4 and 5. a

' -In Figs. 8 and'9, I show a diagrammatic embodi- 1 mer t of the invention and callparticular, attention tothe construction of the heater I 20 which comprises a section'of an exhaust pipe I2I: en'el circled by a tube I22 having an inside diameter greater than the outside diameter or the exhaus't pipe [2| and thereby providing what I termasafety'chamber. The ends,,of the tube I22, are 'welded totheeXhauSt'pipe IZI as tin-j, o dicated at I23 therebyfmaking a pressure tight safety chamber I24; .v t a Mounted upon the tube 22 is another tube I25; which is welded thereto as indicated at I121, pro viding an air heating chamber :I28therebetween and through which an air circulation is maintained; between 'the cold airinl'et 12 9 "and th'e hot air outlet I30, by" some suitable as an air scoop or so.

means such The heat flow path is first through the wall I2I, second, through the safety chamber,

third,through the tube wall I22 and theninto theair heating chamber I20. Tn my practice pf the invention, ,1 utilizecertain extended conduc tive heat transfers'urfaces, Within thechambers I24 and I28, and have'thereby. greatlyincreased the heat transfer ofjsuch heaters, but since the,

, present invention is irrelevant thereto, I have,.for

purposes of simplicity, omitted the same.

Communicating with the safety pressurecham ber I24 is a pressurevconduit I33. to which men-4 matic'pressureis'fed, byjn'iea'ns ofthe' pressure'reducingivalve,20,'=from asuitablesourc ofpii matic' pressure; such'as their compressor for a,

, Micro switch IOIH makes an electric'circuit whenever the operatarias-s4 cylinder I 34 (shown) containing compressed air or any other suitable gas or vapor under pressure; Certain volatile liquids, having proper characteristics, may also beemployed to generate thenec essary vapor pressure." Positioned-between the pressure reducing valve 20 and the pressure 'conduit I3 3, is a restrictor tube I35l 1avingsuch *bore and length that the reduced pressure,'passing from the pressure reducing valve 20 andthrough the restrictor tube I35, can only flow at some certainmaximum flow rate with a given pressure differential betweenthe outlet conduit I36, of the pressure reducing valve 2'0,a'nd the pressure-condu'it'I33. I

Havingkdescribed the component-s, I shall 'now describe the operation as an assembly. Referring to Fig. 8, the inlet, of the pressure reducing valve, is under some certain pneumatic pressure, say 500 lbs. The valve 20 is adjusted to maintain some certain reduced pressure, fed to the conduit I36, say 4 lbs. This 4 lb. pressure now passes through the restrictor tube I35 and into the pressure conduit I33, the safety 'chambenIZQ, the pressure relief valve 40 and the pressure chamber 86 of the automatic valve operator 65. Since the system is presumably leak prooffthe 4 1b. pressure becomes static and the pressure reducing valve 26 automatically closes. The selected 4 lb. pressure is presumptively in excess of any pressure within the exhaust pipe I2I and due to the expulsion of exhaust gases therethrough.

The air plane engine is now started up and the exhaust pipe may reach a temperature of 1600" F. Obviously, the air, within the safety chamber I24, becomes greatly heated and expands. inal 4 lb. pressure may rise to several times that value unless we can bleed off some of the same. We adjust the pressure relief valve 40 for say 6 lbs. Whenever the pressure exceeds6 lbs, the valve 40 bleeds off some of the air pressure. Whenever the pressure decreases below 4 lbs., the valve 20 feeds more air.

The main reason for limiting maximum air pressure, within the safety chamber is due to the fact that exhaust pipes are made of very thin materials and operate at exceedingly high temperatures during which the physical strength is greatly reduced. If for some reason or other the valve 20' should not seat tightly, the air pressures would eventually become suificient to certainly collapse the exhaust pipe, unless we employ the pressure relief valve 40 or some equivalent.

With the airplane still grounded and the engine then shut ofi, the temperatures of the exhaust pipe I 2| approaches the ambient temperature, the air, in the safety chamber I24, cools and contracts, the pressure recedes from 6 lbs/sq. in. to slightly under 4 lbs/sq. in. and the pressure reducing valve opens to maintain the 4 lbs/sq. in. pressure.

During all this time the airplane has been grounded and the ambient pressure (assuming sea level) was 14.7 lbs/sq. in. Now we shall assume that, after the engine is warmed up, the plane takes off. As the flight altitude increases, the ambient pressure decreases and the pressure relief valve 40 continually bleeds off the pressure, to constantly maintain the 6 lbs/sq. in. pressure difierential between the upper and lower sides of the diaphragm 5| of the pressure relief valve 40.

During the descent, of the plane, the ambient pressure continually increases and finally the pressure differential between the upper and lower sides of the diaphragm 29, of the pressure reducing valve 20, reaches a value slightly under 4 The origlbs/sq. in. and the valve '20'opens and continuously feeds air to the system in order zto constantly maintain the 4 lbs/sq. in. pressure differential to whichltis adjusted. r I It -is assumed, in the particular instance, that the valve operator 'issoadjusted that a pneue matic pressure of 3 lbs/sq. inmaintains-thebut terfly valve 63 in wide open position. Whenever the pressure decreases, below 3 lbs./sq."in"., the valve operator 65 then closes the butterfly valve 63 (as shown) and no heated air-can pass to the cabin. a

If the walls of the chamber I24- become punctured, for any reason whatsoever, the pneumatic pressure, within the various elements of the'syse tern, rapidly drops since the volumetric flow; through the restrictor I35, is of a verysmallo-rder and incapable of supplying a sufiicient volume, of pneumatic pressure, to maintain the pred'eter mined 4 lbs/sq. in. pressure.

While the drawings show and the specification explains a particular embodiment ofthe invention, it is to be understood that various modifications may be employed without departing from the spirit and scope of theinvention, which is -to be limited only to the hereto appended claims.

I claim:

1. A hot air heating system utilizing the exhaust gases from an internal combustion engine as a source of heat, comprising: a pipe through which exhaust from the engine flows; a wall surrounding said pipe defining a pressure-tight chamber heated by the exhaust in the pipe; a conduit for air to be heated; a wall defining a heating chamber around the wall of the air tight chamber, communicatively connected to the conduit, and through which a current of air is normally circulated to absorb heat from the air tight chamber prior to its discharge from the conduit, said air tight chamber having no communication with the air in the conduit and the g'asesin the pipe; means for maintaining a pneumatic pressure in said chamber above the pressure of the exhaust gases passing through the pipe; valve-means for controlling the delivery of air from said conduit; and pneumatic-means, au-

tomatically responsive to a predetermined drop in pressure in said air tight chamber for controlling the valve-means to cut off the delivery of air from the conduit.

2. A hot air heating system utilizing the exhaust gases from an internal combustion engine as a source of heat, comprising: a pipe through which exhaust from the engine flows; a wall surrounding said pipe defining a pressure tight chamber heated by the exhaust in the pipe; a conduit for the air to be heated; a wall defining a heating chamber around the wall of the air tight chamber, communicatively connected to the conduit, and through which a current of air is normally circulated to absorb heat from the air tight chamber prior to its discharge from the conduit, said air tight chamber having no communication with the air in the conduit and thegas in the pipe; means for maintaining a pneumatic pressure in said chamber above the pressure of the exhaust gases passing through the pipe, including a pressure reducing valve and restricted flow-means between the reducing valve and the pressure-tight chamber; valve-means for controlling the delivery of air from said conduit; and pneumatic-means, automatically responsive to a predetermined drop in pressure in said air tight chamber, for controlling the valve-means to cut. off the delivery of air from the conduit.

' including a pressure relief valve. V

I 3.;Ahot air heating system utilizing ;the :ex

haust gases froman internal combustion engine as s u e; ofheatgc n sineya pe ro h;

asa source of heat; comprising; a pipe through which exhaust from the engine ;flows;-1a;3va ll surrounding said pipe defining a, pressure .1 tight chamber heated by the ,exhaustin the,,pipe; a"

conduitfor air to be heated; a-wall defininga heating. chamber around the wall .of'the air tight chamber communicatively connected to the conduit, and, through which a current ofairis nornially circulated to absorb heat from the air tight chamber prior to its discharge'from the conduit, said air tight chamber having no communication with the air in the conduit and the gas in the pipe; means for maintaining a pneumatic pressure in said chamber above the pressure of the exhaust, gases passing through the pipe, including a pressure':reducingvalve; valve-means for controlling the delivery of air from said conduit;

pneumatic-means, automatically responsive to a V predetermined drop in pressure in said airtight chamber, for controlling the valve-means to cut off thedelivery of air from the conduit, and

,A4. A'- hot air heating system utilizing the haust gases from an internal combustion engine which exhaust from the engine flows a wall surfrounding" said pipe def ning; a; vpressuretight chamber heated by the exhaust in the pipe; a con-1 duit for air to be heated; a wall defining a heat-. ing chamber around the wallof, the airftight chamber communicatively connected to said; con-i duit,,; and through which a current of air isnor-I mally circulated toabsorbheat from the air tight chamber prior to its discharge through the an; outlet, said air tight chamber being in non-com municating; relation 7 with the airin the conduit; f

and the gas in the pipe; means for maintaining a pneumatic pressure in said'chamber above the f pressure of theexhaust gases, including. a pressure; reducing valve, restricted flow-means be-' tween thereducing valve and said air tight chamber, and a relief valve; valve-mea ns for controlling the delivery of air .from said conduit; and pneumatic-means, automatically responsive to, a predetermined drop in pressure in said airtight chamber, ,for' controlling thevfalve-mean'sto" cut:

011? the delivery of air from the conduit, said means includinga conduit leading from the pres;-

sure relief valve. I 5 a I ANTHONY'F. I- IQE SEL. 

